Just recently found this forum and wanted to say hello. I was an avid SWL growing up, and only recently, after 30+years am getting back into it. I am currently using a Flex 5000 right now but want to fire-up my ole SB-313 that I built and used in the late 70's. I seem to remember it always had a significant lack of sensitivity on 25m, regardless of how well I aligned it. Am wondering if anyone here has a SB-313, and if so, have you ever noticed a lack in sensitivity on 25m?

Hi Gedas. Welcome to the forum...and back to SWLing. I, too, was an avid SWL growing up. As you know, things are very different now in terms of SW broadcasting, but there is still a lot to listen to. Be sure to take a look at the website of the Ontario DX Association. They have a great newsletter each month--look at, among all of them, the World English Survey, which I print out every month. It's like a "TV Guide" for English language broadcasts.

I have no experience with the Heathkit rig. The most modern SWL rig I have is a Drake R8A, but I generally listen using vacuum tube receivers. The older rigs are a lot of fun, have "soul" which the technologically newfangled rigs seem to me to lack, and bring back memories of hunkering over glowing rigs when I was a kid, listening to Radio Nederland.

It's still a wonderful hobby. Thank goodness for Radio Espana Exterior, Radio Romania, Radio Australia, Radio New Zealand, Deutsche Welle, the BBC, Radio Japan, and others!

Hi Tony and thank you for the reply. I checked out and have ear marked the Ontario DX site. Thanks for passing along that information. I like the nice clean layout of the world English summary and will give it a try.

Regarding the SB-313, I knew it was a long shot asking about it but you never know. Fingers are still crossed. I am positive all the alignments were done right and I had made numerous checks to make sure all the right parts where in the right places and yet that one lone band was always a little deaf. Just trying to figure out if it was an original engineering deficiency or something unique to my radio.

I have really fond memories as well as a kid listening with that receiver and all the old wooden console radios I had salvaged earlier from the allies in Detroit as a punk. I'll never forget my first poke of the B+ line going over to the magnet coil on the big speaker ! It is what got me into electronics and even my career I suspect.

Anyway, what sparked my recent SWL interest was when I connected this bit-bucket radio (Flex 5000) to my 40m dipole and took it for a spin on the SWL bands. I was just floored at how nice all the stations sounded and how easy it was to tailor the bandpass to reject nearby stations and other interference. Listening on a set of full fidelity speakers with the right IF bandwidth was a real thrill I had never experienced before. Other than the old console radios I never had a radio that had nice wide filters. The SDR adds nice steep walls to those wide filters making them awesome. The SB-313 was very limited at 6 kHz since it's really a ham rig first (SB-303 clone). First night out listening to All India Radio at 20 over S9 and sounding like a local AM station still has me in awe. Even got a kick listening to Radio Iran rant about the west....made me think of ole PO Box 88 or Radio Havana LOL.

I had a SB303 and recall that a band switch wafer could become bad contact thus causing a loss of sensitivity on one band. It may just need all the contacts, etc cleaned if it receives ok on other bands.

Thanks for the suggestion Chris I will certainly check it out. The radio was like that the day I finished putting it together and aligned it. Back then all the silver on the wafer contacts were nice and shiny but still, maybe something was dorked up for that one band segment and I didn't notice it.

Hi Gedas. Go to "qth.com" and join the Heathkit reflector. If you search the archives, you will probably find your answer. Or, you can just ask the nice folks there. There is always a lot of discussions about the 3XX receivers.....

This is my review old eham reveiw of SB-303, that was an amateur band version of SB-313.Ignacy, NO9E

Got one used with SB-400 some 18 years go. Initially some bands did not work. After alignment, weak signals were barely heard, and overloading was present on some bands, especially on 40m. A 10/20db attentuator solved the overloading problem. A single-transistor amplifier after the crystal filter solved the weak-signal problem. With its narrow SSB (2.1 KHz) and CW (400 Hz), it was a very nice receiver although the CW filter had some blow by. Very nice AGC and very nice audio. It was my favorite receiver but unfortunately the matching SB-400 transmitter was weak. Perhaps if tweeked like the SB-301, e.g., better mic and addition of processor, the transmitter could have been made punchier.

"Hi Gedas. Go to "qth.com" and join the Heathkit reflector. If you search the archives, you will probably find your answer. Or, you can just ask the nice folks there. There is always a lot of discussions about the 3XX receivers.....

ronN4UE"

Hi Ron, that's really great news. Thanks very much for that information......will check it out.73 Gedas, W8BYA

"This is my review old eham reveiw of SB-303, that was an amateur band version of SB-313.Ignacy, NO9E"

Thanks for that Ignacy !Man, I just realized it's been over 25 years since I did my last realignment on my 313. I need to go dig up the manual but I seem to remember that all the bands used the same common amplifier/buffers along the entire chain. If something was messed up on 25m it would sure seem to be an issue on the bands above and or below as well but that isn't the case. Like I said, it's just one band thats down about 10 dB or so (by ear). The rest of the bands were red hot ! No overloading ever, no blow-by, nice and stable and a joy to listen to. All you guys have given me some good info to get me rolling....thanks for helping out and all the info.

I have a SB-313 that I built in the fall of 1974, and it's still looks new, and works fine after almost 40 years! My SB-313's sensitivity was always fine on 25m, and the overall sensitivity was excellent. The only problem I've had with the SB-313 was the LMO stops locked up after having been in storage for a number of years. I had to remove the front panel, and lubricate the stops on the front of the LMO shaft. Other than that, it's been trouble free since the build.

Perhaps you can find someone with a nice old HP signal generator with calibrated output and get some hard numbers. Using the attenuator function gives you a nice weak signal to work with which you can keep reducing as you repeak. I always use the calibrator function as a rough test of sensitivity band to band (keeping in mind that cal signals drop off as you got higher in frequency) and if the RX doesn't have one you can feed one in from another receiver since the cal signal is injected into the front end. Friend of mine calls it the "Vulcan mind meld system". DON'T use a transciever unless you are REALLY sure the transmitter is not going to be triggered! A transceiver with solid state RX and a tube final is OK so long as you DON'T turn the heaters on.

I have a SB-313 that I built in the fall of 1974, and it's still looks new, and works fine after almost 40 years! My SB-313's sensitivity was always fine on 25m, and the overall sensitivity was excellent. The only problem I've had with the SB-313 was the LMO stops locked up after having been in storage for a number of years. I had to remove the front panel, and lubricate the stops on the front of the LMO shaft. Other than that, it's been trouble free since the build.

73Don W9CW

Hi Don, wow this is great. I was wondering if I would ever find another SB-313 user. Your report gives me important information about my rigs issue. Thank you for taking the time to chime in. Last week my employment status was modified for me after 30+ years in the defense electronics industry and I now will have plenty of time to take a good look at my radio. The issue with the LMO is a common one for many of the Heath rigs like the SB-102 etc since they all used the same LMO. A good friend of mine did an extensive investigation of his many years ago and traced the problem to an intermittent ground connection. As I recall all it took was an added ground strap to supplement the existing connection from Heath that was not up to par. I will get with him and ask for the details again and post them here if you are interested.

Perhaps you can find someone with a nice old HP signal generator with calibrated output and get some hard numbers. Using the attenuator function gives you a nice weak signal to work with which you can keep reducing as you repeak. I always use the calibrator function as a rough test of sensitivity band to band (keeping in mind that cal signals drop off as you got higher in frequency) and if the RX doesn't have one you can feed one in from another receiver since the cal signal is injected into the front end. Friend of mine calls it the "Vulcan mind meld system". DON'T use a transciever unless you are REALLY sure the transmitter is not going to be triggered! A transceiver with solid state RX and a tube final is OK so long as you DON'T turn the heaters on.

Hi there and thank you for the reply and information. I like that description "Vulcan mind meld system" LOL. As I mentioned in my post above I will now (unfortunately) have lots of time on my hands and will be able get some actual sensitivity numbers for the different bands for comparison. I do own several recently calibrated HP sig gens, and along with a true RMS reading HP-3400A volt meter getting the required numbers will be a snap.

So just a quick update on the SB-313. Yesterday I brushed off all the dust from the case and front panel and fired it up. It seems I will have to open her up and do some repair work before I can get those sensitivity numbers. No internal 25 kHz or 100 kHz calibrator signals and no over-the-air HF signals with ext antenna connected. Will report back after I fix whatever went south in the last 20-30 years or no use.

I have obtained the whole Heath SB line in the last couple of years with SB-401 / SB-301 at the heart. I wanted them since I always wanted them when they first came out. But I've not progressed much in checking them out yet.

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